You can have a machinist make you a Vega shell. Get a thin shell and he can hollow it out with an end mill. We used to do that years ago, when they were getting hard to find. If you are looking to use a TF904 behind a Chevrolet motor, find one out of a mail truck, as that is what they came in. I don't know how many of them are still around, you will have to look to see what is out there.